Boris Johnson plans to hold a rival inquiry into the future of aviation capacity which will specifically exclude a 3rd runway at Heathrow. The Aviation Commission on aviation capacity, to be chaired by Sir Howard Davies, announced last week, will include Heathrow. Boris’s “call for evidence” will hear from airlines, airport operators, local authorities and aviation experts, on his proposal for a new airport in the Thames estuary or expansion on alternative sites around the capital. The inquiry will last between 9 and 12 months – reporting two years earlier than the Davies Commission. The findings of the Boris inquiry will be presented to the Davies Commission, and Boris has reluctantly decided to cooperate with because of the “realities” of the situation. Windsor MP, Adam Afriyie, is backing Boris in favouring an estuary airport.

Boris Johnson will defy David Cameron by holding a rival inquiry into the future of aviation capacity which will specifically exclude a third runway at Heathrow.

The “call for evidence” will hear from airlines, airport operators, local authorities and aviation experts, gleaning their views on his proposal for a new airport in the Thames estuary or expansion on alternative sites around the capital.

In a move designed to highlight what Mr Johnson has described as the Prime Minister’s “fudge-orama” over the future of aviation, the inquiry will last between nine and 12 months – reporting two years earlier than the Davis Commission which Mr Cameron set up to investigate the same issue.

Unlike the Government’s probe, chaired by Sir Howard Davis, the former head of the Financial Services Authority, Mr Johnson’s investigation will exclude the controversial option of building of a third runway at Heathrow.

Its findings will be presented to the Davis Commission, which will not conclude until after the next election but which Mr Johnson has reluctantly decided to cooperate with because of the “realities” of the situation.

A source close to the Mayor said: “He will be full-throated in his opposition to the third runway at Heathrow both in his submission to the Commission and in public.

“He was serious when he described the Commission as a fudge-orama. Setting up his inquiry will have the double benefit of gathering important views on the future of aviation in the Capital, as well as highlighting how unnecessary it was to kick this issue into the long grass by postponing it until after the election.”

Last week, Mr Johnson responded with fury to the Prime Minister’s decision to use his reshuffle to remove Justine Greening, another London MP who opposes the expansion of Heathrow, from the job of Transport Secretary.

However, his spokesman described as “heavily overstated” reports that he had plotted with Zac Goldsmith, the millionaire Richmond MP who is a leading campaigner against the third runway, to trigger a by-election in the seat in south-west London, in which Mr Johnson would stand.

In theory, this would allow him to return to the Commons as a credible leadership challenger.

While the subject was raised at a meeting between the two men to discuss tactics over Heathrow, the spokesman said, it came up in a conversation about “tea room tittle tattle” among Tory MPs in the Commons, and was “laughingly dismissed” by both.

Mr Johnson’s campaign was given a boost after Vince Cable, the Liberal Democrat Business Secretary, ruled out a third runway at Heathrow, and a senior backbencher in his own party supported the Mayor’s Thames Estuary plan.

Mr Cable told the BBC’s Andrew Marr Show that the weight of opposition to the third runway was overwhelming.

“There is an absolutely clear coalition commitment not to expand Heathrow,” he said. “There is a very formidable political coalition against it: my party is totally opposed, Boris Johnson and the London Conservatives are opposed, the Labour Party seems to be moving against it.

“It is not going to happen so the value of this commission the Prime Minister had been talking about is looking at alternatives.”

In an article (today) for the Telegraph, Mr Afriyie said: “The country is in desperate need of policies that will create jobs and economic growth. (see link )

“As an island trading nation we need a bold solution for aviation that shows leadership.

“A single short runway at Heathrow would be a half-hearted and timid step. It would be temporary sticking plaster when we need to build five or 10 new runways to remain competitive over the forthcoming decades.

“With a major new coastal airport flights could operate 24/7 without disturbing anyone. A high-speed rail link would whisk passengers to central London and the national transport network within the hour.”

Andrew Pendleton, of Friends of the Earth, welcomed Mr Cable’s announcement. He said: “Aviation policy mustn’t be driven by the economics of desperation and misleading industry spin – there’s no need for any new airports or runways in the south east.

“What’s urgently required is a sustainable transport strategy that safeguards local communities and the environment and plays its part in tackling climate change.”

Meanwhile, another Conservative MP, Col Bob Stewart, disclosed yesterday that he had been approached by two unnamed Tories and asked to stand as a stalking horse candidate for a serious challenger to Mr Cameron, presumably Mr Johnson.

The MP for Beckenham said that he refused the suggestion, which was put to him before the summer break, telling the plotters to “get lost”.

David Mellor, the former Conservative cabinet minister, told Sky News that the events showed how “poisonous” relations within the party had become.